Converter and power converter that becomes it with the converter

ABSTRACT

A converter includes a converter circuit  1  having a plurality of bridge-connected semiconductor switching devices for converting AC power into DC power, a smoothing condenser connected in parallel to the DC side of the converter circuit and a current detector provided in a condenser circuit to control a condenser current flowing through the smoothing condenser to be a set value. The condenser current is controlled to be the set value (e.g. zero) to thereby reduce the capacity of the smoothing condenser and make the converter small.

BACKGROUND OF THE INVENTION

The present invention relates to a converter that converts AC(alternating current) power into DC (direct current) power and a powerconverter that becomes it with the converter to produce AC power havingany frequency and voltage.

In a driving system of an electric motor, it is necessary to change afrequency of AC power to any frequency in order to control a rotationalspeed of the motor freely and a power converter using semiconductorswitching devices such as insulated gate bipolar transistors (IGBTs) isused therefor. Most of such power converters each include a converterfor converting AC power into DC power and an inverter for converting theDC power produced by the converter into AC power having any frequencyand voltage.

However, since a DC voltage is varied due to unequalness of the DC powertransferred between the converter and the inverter, a smoothingcondenser is provided in a DC circuit connecting therebetween tosuppress the variation of the DC voltage. Generally, an electrolyticcondenser used as the smoothing condenser is very large in the volume ascompared with semiconductor switching devices and accordingly thepercentage of the volume of the smoothing condenser occupying the powerconverter is increased. Therefore, if the capacity of the smoothingcondenser is reduced, the power converter can be made small.

Heretofore, in order to reduce the capacity of the smoothing condenser,Japanese Patent Publication JP-A-2003-102177, for example, disclosesthat an input current and a DC input current based on a current commandfor an inverter are presumed and an AC input current of the converter iscontrolled so that a DC output current of a converter is equal to the DCinput current of the inverter. Further, Japanese Patent PublicationJP-A-7-79567 discloses that an active filter is connected in parallel toa smoothing condenser and a compensation current of the active filter iscontrolled so that DC voltage variation is absorbed.

SUMMARY OF THE INVENTION

However, an apparatus disclosed in JP-A-2003-102177 requires a lot ofdetectors for detecting AC input current, DC voltage, AC output current,rotational speed and the like and accordingly there sometimes occurs aproblem that the volume of the apparatus is increased due to addeddetectors besides making small the smoothing condenser.

Further, an apparatus disclosed in JP-A-7-79567 requires detectors fordetecting input current, AC voltage, DC voltage and DC current in orderto control the compensation current and there is a problem that theapparatus is made large and control is also complicated. Particularly,the AC voltage detector and the input current detector have a referencepotential different from that of the DC voltage detector andaccordingly, an insulation circuit is required. Further, since a circuitconstant of the active filter depends on a circuit constant on the inputside, there is no generality.

It is a first object of the present invention to provide a converterthat can reduce the capacity of a smoothing condenser connected to a DCcircuit without increasing the number of detectors.

Furthermore, it is a second object of the present invention to provide asmall-sized and packaged power converter including an inverter and theconverter of the present invention used as a DC source.

In order to achieve the first object, the converter according to thepresent invention comprises a converter circuit including a plurality ofbridge-connected semiconductor switching devices for converting AC powerinto DC power, a smoothing condenser connected in parallel to DC side ofthe converter circuit and a current detector provided in a condensercircuit to control a condenser current flowing through the smoothingcondenser to be a set value.

More particularly, the condenser current flowing through the smoothingcondenser is detected to control the condenser current to be the setvalue (e.g. zero), so that the capacity of the smoothing condenser canbe reduced and the converter can be made small. In order to control thecondenser current to be the set value, the plurality of bridge-connectedsemiconductor switching devices constituting the converter circuit maybe controlled. Concretely, it can be realized by providing q-axiscurrent control means that controls a q-axis current component of the DCcurrent of the converter circuit so that a difference between thecondenser current and the set value is reduced.

Further, in order to control the converter, information of the ACcurrent on the input side is required usually, although when an AC inputcurrent of the converter circuit is detected, the number of detectorsare increased. Accordingly, it is considered that the DC current of theconverter (or inverter) contains information about the AC current and aDC current detector for detecting the DC current of the convertercircuit is provided. Calculation means for calculating the AC current onthe input side of the converter circuit on the basis of the DC currentdetected by the DC current detector and operation states of theplurality of semiconductor switching devices is provided to make itpossible to suppress the number of detectors from being increased.

Moreover, it is desired to provide compensation means for calculatingthe q-axis current component of the AC current on the basis of the ACcurrent calculated by the calculation means of the AC current on theinput side and feeding back the q-axis current component of the ACcurrent to correct a q-axis current command value of the q-axis currentcontrol means.

The condenser current detector and the DC current detector can use shuntresisters.

Further, the converter of the present invention is preferably ofpackaged type comprising a main circuit board in which a convertercircuit including a plurality of bridge-connected semiconductorswitching devices for converting AC power into DC power is formed, acontroller board in which a controller for controlling the plurality ofsemiconductor switching devices is formed, a package in which the maincircuit board is provided and on which the controller board is placed toconnect therebetween, an external terminal for a smoothing condenserconnected in parallel to DC side of the converter circuit and which ismounted at periphery of the package and a current detector connectedbetween the external terminal and the converter circuit. Consequently,the capacity of the smoothing condenser can be reduced and the wholeconverter apparatus can be made small.

In order to achieve the second object, the power converter of packagedtype according to the present invention comprises a main circuit boardin which two sets of power converter circuits each including a pluralityof bridge-connected semiconductor switching devices are connected toeach other through a DC circuit, a controller board in which acontroller for controlling the plurality of semiconductor switchingdevices for the two sets of power converter circuits is formed and apackage in which the main circuit board is provided and on which thecontroller board is placed to connect therebetween. The package includestwo sets of AC terminals connected to the two sets of power convertercircuits, respectively, an external terminal for a smoothing condenserconnected in parallel to the DC circuit and an external terminalconnected to the controller and all the terminals are disposed atperiphery of the package. The main circuit board includes at least twocurrent detectors for detecting a DC current flowing through theexternal terminal for the smoothing condenser and DC currents in thepower converter circuits.

As configured above, the effects of the converter according to thepresent invention can be attained and the power converter including theconverter and the inverter can be made small without increasingdetectors as described below. That is, the junction of the DC circuitconnecting two sets of power converter circuits and the smoothingcondenser is a so-called Y connection. Accordingly, it is not alwaysnecessary to detect the DC current flowing through the smoothingcondenser and the DC currents flowing through the two sets of powerconverter circuits and if two of these currents are detected, theremaining one current can be calculated. In other words, there may beprovided current calculation means for calculating a current in a partwhere a current detector is not provided on the basis of two currentvalues detected by at least two current detectors. This currentcalculation means can be realized by calculation means such as amicrocomputer and a digital signal processor (DSP). It is possible notto provide a detector for a condenser current flowing through thesmoothing condenser and in this case the condenser current can becalculated on the basis of a difference between the converter DC currentand the inverter DC current.

Particularly, since electric power containing all losses produced in theportion from the smoothing condenser to the load side is supplied to thepower converter circuit side corresponding to the converter, the DCcurrent on the converter side is larger than that on the inverter side.Further, since only switching ripple in the power converter circuitflows through the smoothing condenser basically, the absolute value ofthe current flowing through the smoothing condenser is very small ascompared with the two power converter circuits. Accordingly, it isdesired to provide two current detectors for detecting the DC current ofthe power converter circuit corresponding to the inverter and thecondenser current of the smoothing condenser. Consequently, the loss ofthe current detector can be reduced.

Further, in the power converter of packaged type according to thepresent invention, the controller controls one of the power convertercircuits, that is, the plurality of semiconductor switching devices ofthe power converter circuit corresponding to the converter to controlthe condenser current to be the set value. Moreover, when the currentdetectors are configured by means of shunt resistors, an amplifier suchas an operational amplifier (OP) can be used to convert currentinformation into an electrical signal simply. In this case, it isdesired to connect one ends of two to three current detectors to thesame potential. That is, one ends of the current detectors can beconnected in common to the negative line (N-line) of the smoothingcondenser as a reference potential to form the configuration that is notinfluenced by scattered detection values of the current detectors due todisposition of semiconductor switching devices and wiring resistance andvariation of the reference potential due to noise. This configuration isthe same even in the case where the shunt resistor is used and even inthe case where non-contact type current sensor is used.

In the power converter of packaged type according to the presentinvention, the controller includes decision means for deciding an ACterminal connected to an AC power supply on the basis of a detectedcurrent of the at least one current detector and means for controllingto operate the power converter circuit connected to the AC power supplyas a converter and to operate the other power converter circuit as aninverter on the basis of decision result of the decision means. In otherwords, when the power supply is turned on, an initial charging currentflows through the smoothing condenser and accordingly this initialcharging current can be observed to thereby decide which of externalterminals connected to two sets of power converter circuits the AC powersupply is connected to.

After the initial charging current is ended or disappears, thecontroller includes, instead of observing the initial charging current,decision means for deciding an AC terminal connected to an AC powersupply on the basis of detected currents of the two current detectorsafter the semiconductor switching devices of lower arms for one of thetwo sets of power converter circuits are turned on and means forcontrolling to operate the power converter circuit connected to the ACpower supply as a converter and to operate the other power convertercircuit as an inverter on the basis of decision result of the decisionmeans.

As described above, since the power converter of packaged type accordingto the present invention can configure the converter and the invertersymmetrically about the smoothing condenser, the power converter can beoperated even if which of the power converter circuits the AC powersupply is connected to. Accordingly, the degree of freedom such asarrangement of the power converter and rearrangement suitable for spacethereof is improved remarkably.

The power converter of packaged type according to the present inventioncan be incorporated as one component of a system for driving a motor fora compressor in a packaged air-conditioner, for example.

According to the present invention, there can be realized the converterthat can reduce the capacity of the smoothing condenser connected to theDC circuit without increasing detectors.

Further, the power converter including the inverter that uses theconverter of the present invention as a DC power supply can be madesmall and be packaged.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a basic configuration diagram illustrating an embodiment of apower converter that uses a converter according to the presentinvention;

FIG. 2 is an exploded perspective view of a package of the powerconverter shown in FIG. 1;

FIG. 3 is a detailed configuration diagram illustrating the powerconverter of FIG. 1;

FIG. 4 is a detailed configuration diagram illustrating convertercircuit control means used in the power converter of FIG. 3;

FIG. 5 is a diagram explaining operation of AC current reproductionmeans of FIG. 4;

FIG. 6 is a detailed configuration diagram illustrating inverter circuitcontrol means used in the power converter of FIG. 3;

FIG. 7 is a detailed configuration diagram illustrating a powerconverter according to another embodiment of the present invention;

FIG. 8 is a detailed configuration diagram illustrating a powerconverter according to another embodiment of the present invention;

FIG. 9 is a diagram explaining an example of a method of deciding aterminal to which a power supply is connected in the embodiment of FIG.8;

FIG. 10 is a diagram explaining another example of a method of decidinga terminal to which a power supply is connected in the embodiment ofFIG. 8;

FIG. 11 is a diagram explaining operation of the decision method of FIG.10;

FIG. 12 is a diagram explaining operation of the decision method of FIG.10;

FIG. 13 is a detailed configuration diagram illustrating a powerconverter according to another embodiment of the present invention; and

FIG. 14 is a schematic diagram illustrating an outdoor unit of anair-conditioner in which the power converter of the present invention isapplied to drive a compressor thereof.

DESCRIPTION OF THE EMBODIMENTS

The present invention is now described with reference to embodiments.

Embodiment 1

FIG. 1 is a basic configuration diagram illustrating an embodiment of apower converter that uses a converter according to the present inventionto produce AC power having any frequency and voltage. FIG. 2 is anexploded perspective view of a package of the power converter shown inFIG. 1. FIG. 3 is a detailed configuration diagram illustrating thepower converter of FIG. 1. FIG. 4 is a detailed configuration diagramillustrating converter circuit control means used in the power converterof FIG. 3. FIG. 6 is a detailed configuration diagram illustratinginverter circuit control means used in the power converter of FIG. 3.

As shown in FIG. 1, the power converter 14 includes, broadly divided, apower unit 9 and a control unit 11. The power unit 9 includes aconverter circuit 1, a smoothing condenser 10 connected across the DCoutput of the converter circuit 1 and an inverter circuit 2 connected tothe DC output of the converter circuit 1. The converter circuit 1 isconnected to an AC power supply 6 through reactors 7 and converts ACpower supplied through the reactors 7 into DC power. The invertercircuit 2 converts the DC power supplied from the converter circuit 1through the smoothing condenser into AC power to supply the AC power toa motor 8.

Further, a current detector 3 for detecting a current flowing throughthe DC side of the converter 1 and a current detector 4 for detecting acurrent flowing through the smoothing condenser 10 are provided in thenegative side (N-line) of a DC circuit that is connected between theconverter circuit 1 and the inverter circuit 2. Moreover, a voltagedetector 20 for detecting a DC voltage across the smoothing condenser 10is provided. On the other hand, the control unit 11 includes acontroller for controlling the converter circuit 1 and the invertercircuit 2. The control unit 11 produces pulse signals 12 and 13 on thebasis of current information detected by the current detectors 3 and 4and drives the converter circuit 1 and the inverter circuit 2 by thepulse signals.

As shown in FIG. 2 as the exploded perspective view, the power converter14 can incorporate the power unit 9 and the control unit 11 into asingle module to be integrally formed. More particularly, the power unit9 composed of the converter circuit 302 and the inverter circuit 303that are connected through the DC circuit is mounted on a main circuitboard 301 made of aluminum and the main circuit board 301 is mountedwithin a depression portion of a package 300 formed into a square. Onthe other hand, the control unit 11 including one-chip microcomputer 16for controlling a plurality of semiconductor switching devices of thepower unit 9 is mounted on a sub-board 17 and the sub-board 17 is placedon one side of the package 300 so that the control unit 11 is connectedto the power unit 9 to thereby form a packaged-type power converter 14.The microcomputer 16 may use a digital signal processor (DSP).

The package 300 is equipped with at its periphery AC terminals 305 aconnected to the converter circuit 302, AC terminals 305 c connected tothe inverter circuit 303, external terminals 305 b connected to thesmoothing condenser and external terminals 306 for connecting theconverter circuit 302 and the inverter circuit 303 to the controller ofthe control unit 11. That is, in the embodiment, the smoothing circuitis structured to be connected externally. Further, the sub-board 17 isequipped with connectors 307 connected to external controller such ashigher-rank controller. Moreover, the main circuit board 301 is equippedwith two current detectors for detecting a current flowing through theexternal terminals 305 b for the smoothing condenser and a currentflowing through the DC side of the converter circuit 302. As apparentfrom the DC circuit of FIG. 1, since the DC circuit of N-line and thesmoothing condenser are connected into so-called Y-connection, only twoof three current detectors for detecting the current flowing through thesmoothing condenser, the current flowing through the DC side of theconverter circuit 302 and the current flowing through the DC side of theinverter circuit 303 can be provided to thereby calculate the remainingone current.

As shown in FIG. 2, in the packaged-type power converter 14 of theembodiment, the power system including the semiconductor switchingdevices and the control system including the microcomputer 16 and thelike are disposed separately from each other so that the control systemis not influenced by noise generated from the power system. Further, thesemiconductor switching devices mounted on the main circuit board 301are not limited to bare-chips but packaged parts may be mounted insteadthereof. Moreover, a shield plate can be disposed between thesemiconductor switching devices of the power system and themicrocomputer 16 of the control system, so that the control system ofthe microcomputer 16 and the like can be mounted on single main circuitboard 301 together with the semiconductor switching devices of the powersystem. Furthermore, when it is desired to increase or reduce thecapacity of the power converter 14, components can be exchanged easilyso that only the power unit, for example, is changed and simplicity ofmaintenance is improved.

FIG. 3 schematically illustrates the power converter 14 shown in FIG. 1in detail. As shown in FIG. 3, the converter circuit 1 and the invertercircuit 2 use insulated gate bipolar transistors (IGBTs) as theplurality of bridge-connected semiconductor switching devices. The IGBTsof the converter circuit 1 constitute upper and lower arms or sides forR-, S- and T-phases. The junctions of the upper and lower arms for thephases are connected to the AC power supply 6 through the reactors 7.The converter circuit 1 amplifies first PWM (pulse width modulation)signals 12 by means of a first driver circuit 18 and applies theamplified PWM pulse signals 12 a to 12 c to the IGBTs for the phases.The IGBTs make switching operation in response to the PWM pulse signals12 a to 12 c. The converter circuit 1 is to convert AC power into DCpower in response to the switching operation and make wave-shaping ofthe input current and boosting of the DC voltage. In the embodiment,there is not provided a detector for the AC input current, although theAC input current is calculated on the basis of the DC current detectedby the current detector 3 connected on the way of passage of the currentflowing through the DC side of the converter circuit 1 and the operationstates of the IGBTs of the upper and lower arms for the R-, S- andT-phases. Concrete calculation method thereof will be described later.Further, the converter circuit 1 can make regeneration operation that DCpower is converted into AC power to return it to the AC power supply 6.

The smoothing condenser 10 smoothes the DC power produced by theconverter circuit 1. The condenser current flowing through the smoothingcondenser 10 is detected by the current detector 4.

The IGBTs of the inverter circuit 2 constitute upper and lower arms orsides for U-, V- and W-phases in the same manner as the convertercircuit 1 and the junctions of the upper and lower arms for the phasesare connected to the motor 8. The motor 8 has a rotor made of apermanent magnet and a plurality of windings disposed around the rotorto form AC magnetic field. The inverter circuit 2 amplifies PWM pulsesignals 13 by means of a driver circuit 19 and applies the amplified PWMpulse signals to the IGBTs for the phases. The IGBTs make switchingoperation to thereby convert the DC power smoothed by the smoothingcircuit 10 into the AC power having a designated voltage and frequencyand the converted AC power is supplied to the motor 8. In theembodiment, a detector for detecting an AC current flowing through themotor 8 is not provided, although a current flowing through the DC sideof the inverter circuit 2 is calculated on the basis of the currentsdetected by the current detectors 3 and 4 and the AC current iscalculated on the basis of the calculated current and the operationstates of the IGBTs of the upper and lower arms for the U-, V- andW-phases. Concrete calculation method thereof will be described later.

The controller 11 includes an analog-to-digital (A-D) conversion means21, converter circuit control means 22 and inverter circuit controlmeans 23. The A-D conversion means 21 includes an amplifier such as anoperational amplifier for amplifying signals from the current detectors3 and 4 and an analog-to-digital (A-D) converter that operates whileusing any of the PWM signals 12 and the PWM signals 13 as a timingsignal for receiving an analog value. The A-D converter hassample-and-hold function and A-D conversion function and is formed in asingle semiconductor integrated circuit constituting the controller 11.The A-D converter converts the received analog value into a digitalvalue and supplies the digital value to the converter circuit controlmeans 22 and the inverter circuit control means 23.

The converter circuit control means 22 is supplied with a DC voltage Edcdetected by the voltage detector 20 that detects the voltage across thesmoothing condenser 10, a converter DC current idc1 detected by thecurrent detector 3 and a condenser current ic detected by the currentdetector 4 through the A-D conversion means 21 and produces the PWMsignals 12 to supply the PWM signals 12 to the driver circuit 18 of theconverter circuit 1 so that the condenser current ic is minimized and apredetermined DC voltage is produced. Further, the inverter circuitcontrol means 23 receives the converter DC current idc1 detected by thecurrent detector 3 and the condenser current ic detected by the currentdetector 4 through the A-D conversion means 21 to calculate an inverterDC current idc2 and produces the PWM signals 13 to supply the PWMsignals 13 to the driver circuit 19 of the inverter circuit 2 so thatthe AC power having the designated frequency and voltage is produced.Further, the converter circuit control means 22 and the inverter circuitcontrol means 23 are configured to be able to transmit and receivevarious data therebetween, so that cooperation control between theconverter circuit 1 and the inverter circuit 2 can be attained.

In this connection, when shunt resistors are used as the currentdetectors 3 and 4, one ends of the two shunt resistors are connected tothe N-line side connected to the smoothing condenser 10 and the otherends thereof are connected to the A-D conversion means 21. Consequently,even if the reference potential is varied due to external noise or thelike, the relative relation between the two current detectors is notchanged and accordingly relative error can be reduced. Further, thecurrent detectors 3 and 4 are not limited to the shunt resistors and canuse current transformers (CT), Hall-effect elements or the like. Even inthis case, detection of currents can be made using the same potential asthe reference potential.

FIG. 4 schematically illustrates the converter circuit control means 22constituting the converter that is characteristic of the presentinvention. The converter circuit control means 22 includes a voltageloop for calculating a voltage command value and a phase loop forpresuming a phase of the power supply.

The voltage loop for calculating the voltage command includes currentreproduction means 100 for calculating three-phase AC currents for R-,S- and T-phases on the basis of the converter DC current idc1 of theconverter circuit 1, a voltage compensator or voltage controller 101 forsuppressing a deviation between the DC voltage Edc and a DC voltagecommand value Edc* to zero, a current compensator or current controller102 for suppressing a deviation between the condenser current ic flowingthrough the smoothing condenser 10 and a condenser current command valueic* to zero, a 3Φ/dq converter 103 for converting the three-phase ACcurrents into d1-axis current and q1-axis current by means of dqconversion, and a voltage command preparation unit 104 for preparingvoltage command values (Vdc1* and Vqc1*).

Further, the phase loop for presuming the phase of the power supplyincludes a power supply phase presumption unit 107 for presuming thephase of three-phase AC power supply on the basis of output of the 3Φ/dqconverter 103, a phase compensator 108 for suppressing a deviationbetween a power supply phase error Δθs presumed by the power supplyphase presumption unit 107 and a power supply phase error command valueΔθs* to zero and a power supply phase calculator 109 for calculating thephase of the power supply. In FIG. 4, the condenser current commandvalue ic*, the DC voltage command value Edc*, the power supply phaseerror command value Δθs* and power supply angular speed command valueωs* are previously given in the converter circuit control means 22.However, the present invention is not limited thereto but the abovecommand values may be supplied externally by means of higher-rankcontrol means, communication or the like.

The voltage command values Vdc1* and Vqc1* for d1- and q1-axes producedby the voltage command preparation unit 104 are coordinate-convertedinto voltage command values for three-phase axis by means of a dq/3Φconverter 105 on the basis of the power supply phase θs* calculated bythe power supply phase calculator 109 to be supplied to a pulsegenerator 106. The pulse generator 106 prepares the PWM pulse signals 12on the basis of the voltage command values to supply the PWM pulsesignals to the driver circuit 18.

Next, operation of the converter circuit control means 22 is described.The condenser current ic detected by the current detector 4 is convertedinto a digital signal by the A-D conversion means 21 and is supplied tothe converter circuit control means 22. The condenser current ic iscompared with the condenser current command ic* in a subtractor 111 anda difference Δic therebetween is supplied to the current compensator102. The condenser current command ic* is usually zero. The currentcompensator 102 makes proportional control, for example, and produces acommand value of a q1-axis current component for compensating orsuppressing the difference Δic to zero. Consequently, the condensercurrent ic can be controlled to be minimum to thereby reduce thecapacity of the smoothing condenser 10.

On the other hand, the DC voltage Edc detected by the voltage detector20 is converted into a digital signal by the A-D conversion means 21 andis supplied to the converter circuit control means 22. The supplied DCvoltage Edc is compared with the DC voltage command value Edc* in asubtractor 112 and a difference ΔEdc therebetween is supplied to thevoltage compensator 101. The voltage compensator 101 makes integralcontrol, for example, and produces command value of q1-axis currentcomponent for compensating or suppressing the difference ΔEdc to zero.Consequently, the DC voltage Edc can be controlled to a predeterminedvalue. Outputs of the current compensator 102 and the voltagecompensator 101 are added to thereby obtain a q1 c-axis current commandiq1 c* and this q1 c-axis current command iq1 c* is supplied to asubtractor 113.

The subtractor 113 is supplied with a q1-axis current iq1 c converted bythe 3Φ/dq converterr 103 on the basis of the AC input current reproducedby the current reproduction means 100. The subtractor 113 calculates adifference between the current command iq1 c* and the q1-axis currentiq1 c and supplies the difference to the voltage command preparationunit 104 as a q1-axis current command iq1**.

The current reproduction means 100 is now described. The currentreproduction means 100 is supplied with the converter DC current idc1detected by the current detector 3 and converted into the digital signalby the A-D conversion means 21. The current reproduction means 100reproduces the AC input current on the basis of the supplied converterDC current idc1 and the PWM pulse signals 12 representing the operationstates of the IGBTs of the converter circuit 1 as shown in FIG. 5. Thatis, as shown in FIG. 5, the converter DC current idc1 detected by thecurrent detector 3 is varied in response to switching states of theIGBTs for respective phases. A reference triangular wave 121,three-phase voltage command signals 120, PWM pulse signals 12 forrespective phases, input currents 122 a to 122 d for respective phasesand DC current idc1 flowing through the current detector 3 are shown inFIG. 5. In FIG. 5, when drive signals 123 a to 123 c of IGBTs forrespective phases are high level, the upper arms for respective phasesare on and when the drive signals are low level, the lower arms forrespective phases are on. In FIG. 5, for clarification, dead time is notshown, although practically dead time is provided to prevent the upperand lower arms for respective phase from being short-circuited.

In FIG. 5, T-phase input current of opposite polarity can be observed insections A and D that the only lower arm for T-phase is on and the upperarms for R- and S-phases are on. Further, R-phase input current of thesame polarity can be observed in sections B and C that the lower armsfor S- and T-phases are on and the only upper arm for R-phase is on. Inthis manner, the converter DC currents in respective sections can beobserved and combined to thereby reproduce the three-phase inputcurrents.

The reproduced input currents are supplied to the 3Φ/dq converter 103.The 3Φ/dq converter 103 coordinate-converts the three-phase AC currentreproduced as the input current into the d1-axis current and the q1-axiscurrent in accordance with the power supply phase θs* and produces thecoordinate-converted d1 c-axis current id1 c and q1 c-axis current iq1c. The d1 c-axis current id1 c is supplied to a subtractor 114, whichcalculates a difference between the d1 c-axis current id1 c and a d1c-axis current command id1 c* to produce a d1-axis current command id1**and supply it to the voltage command preparation unit 104.

The voltage command preparation unit 104 makes vector operation inaccordance with the following expressions (1) on the basis of thed1-axis current command id1**, the q1-axis current command iq1** and thepower supply angular speed command ωs* previously given to produced1-axis voltage command Vd1* and q1-axis voltage command Vq1* and supplythem to the dq/3Φ converter 105 and the power supply phase presumptionunit 107.Vd 1*=R 1 c×id 1**−ωs*×Lq 1×iq 1**Vq 1*=R 1 c×iq 1**+ωs*×Ld 1×id 1**+ωs*Ka  (1)where R1 c is a winding resistance of the reactor 7, Ld1 an inductanceof the reactor 7 for the d1-axis, Lq1 an inductance of the reactor 7 forthe q1-axis and Ka a phase voltage of the power supply.

The dq/3Φ converter 105 coordinate-converts the d1-axis voltage commandVd1* and the q1-axis voltage command Vq1* into three-phase voltagecommand signals 120. The pulse generator 106 generates the PWM pulsesignals 12 for driving the IGBTs for the respective phases of theconverter circuit 1 on the basis of the three-phase voltage commandsignals 120.

On the other hand, the power supply phase presumption unit 107 uses thed1 c-axis current idc1 and the q1 c-axis current iqc1 supplied from the3Φ/dq converter 103 and the d1-axis voltage command Vd1* and the q1-axisvoltage command Vq1* supplied from the voltage command preparation unit104 to calculate an error Δθsc between the power supply phase θs of theAC power supply 6 and a current AC power supply phase θsc held by theconverter circuit control means 22 as a deviation from the d1-axis. Theerror Δθsc is subtracted from the power supply phase error command Δθs*and a difference thereof is subjected to proportional-plus-integralcontrol in the phase compensator 108, so that the phase compensator 108produces an angular speed error Δωsc. The angular speed error Δωscproduced by the phase compensator 108 is added to the power supplyangular speed command ωs* to calculate the sum thereof. The sum isintegrated by the power supply phase calculator 109, so that the powersupply phase θs can be presumed. The presumed power supply phase θs issupplied to the 3Φ/dq converter 103 and the voltage command preparationunit 104 to be used in respective operations of the 3Φ/dq converter 103and the voltage command preparation unit 104.

As described above, in the converter circuit control means 22, the errorΔθsc between the power supply phase θs of the AC power supply 6 and thepower supply phase θsc held by the converter circuit control means 22 iscalculated and the power supply command Δθs* is corrected by means ofthe phase locked loop (PLL) method so that the calculated power supplyphase error Δθsc is reduced to zero to thereby presume the power supplyphase θsc. The correction is made by adding the angular speed error Δωsto the power supply angular speed command ωs*.

On the other hand, as shown in FIG. 6, the inverter circuit controlmeans 23 is supplied with the inverter DC current idc2 of the invertercircuit 2. The inverter DC current idc2 can be calculated as adifference between the converter DC current idc1 and the condensercurrent ic detected by the current detectors 3 and 4, respectively, bythe following expression (2). This calculation can be made before theA-D conversion or after A-D conversion of the A-D conversion means 21.As described above, in the embodiment, one current detector can bedeleted. Particularly, since only switching ripple in the powerconverter circuit flows through the smoothing condenser 10 basically,loss in current detection is small as compared with the provision of thecurrent detector that directly detects the inverter DC current idc2 andaccordingly high efficiency can be attained.idc 2=idc 1−ic  (2)

The inverter circuit control means 23 includes current reproductionmeans 200 for calculating three-phase AC currents for U-, V- andW-phases on the basis of the inputted inverter DC current idc2, a 3Φ/dqconverter 201 for converting the three-phase AC currents into a d2 q2-axis current by dq conversion, a voltage command (Vd2 c* and Vq2 c*)preparation unit 203, a dq/3Φ converter 204 for coordinate-converting d2q 2-axis into three-phase axes, a pulse generator 205 for generating PWMpulse signals, a magnetic pole position presumption unit 206, a magneticpole position compensator 207 for suppressing a deviation between themagnetic pole position error Δθc presumed by the magnetic pole positionpresumption unit 206 and a magnetic pole position error command Δθc*(=0) to zero and a magnetic pole position calculator 208 for calculatingthe magnetic pole position. The basic configuration of the invertercircuit control means 23 is the same as the converter circuit controlmeans 22 and the inverter circuit control means 23 includes a voltageloop for calculating a voltage command value and a magnetic poleposition loop for presuming the magnetic pole position.

The voltage loop for calculating the voltage command value is firstdescribed. The current reproduction means 200 is supplied with theinverter DC current idc2 and reproduces the three-phase AC currents forU-, V- and W-phases. In the reproduction method, as described withreference to FIG. 5, the W-phase input current of the opposite polaritycan be observed in sections that the only lower arm for W-phase is onand the upper arms for U- and V-phases are on. Further, the U-phaseinput current of the same polarity can be observed in sections that thelower arms for V- and W-phases are on and the only upper arm for U-phaseis on. The reproduced three-phase AC currents are coordinate-convertedinto d2 cq 2 c-axis currents (id2 c and iq2 c) by the 3Φ/dq converter201. The coordinate-converted q2 c-axis current is filtered by alow-pass filter (LPF) 202 to thereby obtain q2-axis current commandiq2*. The voltage command preparation unit 203 makes vector operation inaccordance with the following expressions (3) on the basis of d2-axiscurrent command id2*, q2-axis current command iq2* and angular speedcommand ωi* and produces d2-axis voltage current Vd2* and q2-axisvoltage command Vq2* to supply them to the dq/3Φ converter 204 and themagnetic pole position presumption unit 206.Vd 2*=R 1 i×id 2**−ωi*×Lq 2×iq 2*Vq 1*=R 1 i×iq 2**+ωi*×Ld 2×id 2**+ωi*×Ke  (3)where R1 i is a winding resistance of the motor 8, Ld2 an inductance ford2-axis, Lq2 an inductance for q2-axis and Ke a power generationconstant.

The dq/3Φ converter 204 coordinate-converts d2-axis voltage command Vd2*and q2-axis voltage command Vq2* into three-phase inverter voltagecommand signals 220. The pulse generator 205 produces PWM pulse signals13 for driving the IGBTs for respective phases on the basis of thethree-phase inverter voltage command signals 220. The magnetic poleposition loop for presuming the magnetic pole position is configured inthe same manner as the phase loop in the converter circuit control means22 with the exception that only control constants are changed.

As an example of cooperation operation between the converter circuit 1and the inverter circuit 2, there is delivery or transfer of the DCvoltage command Edc*. The DC voltage Edc required by the invertercircuit 2 can be easily calculated by the voltage command preparationunit 203 of the inverter circuit control means 23. Accordingly, the DCvoltage Edc calculated by the voltage command preparation unit 203 isdelivered or transferred to the converter circuit control means 22 tovary the DC voltage command Edc* in the converter circuit control means22, so that the DC voltage command Edc* is made large when load is heavyand the DC voltage command Edc* is made small when load is light tothereby make it possible to improve the efficiency of the systemincluding the converter circuit 1, the inverter circuit 2 and the motor9 and realize saving of energy.

In the embodiment, the converter that is characteristic of the presentinvention is used to configure the power converter used to drive themotor by way of example. However, the present invention is not limitedthereto and the power converter including only the converter can beconfigured without the provision of the inverter. Further, only theconverter can be packaged.

Embodiment 2

A second embodiment of the power converter according to the presentinvention is shown in FIG. 7. The second embodiment is different fromthe embodiment of FIG. 1 in that a current detector 5 for directlydetecting the inverter DC current idc2 of the inverter circuit 2 isprovided in addition to the current detector 3 for detecting theconverter DC current idc1 of the converter circuit 1 and the currentdetector 4 for detecting the condenser current ic flowing through thesmoothing condenser 10. According to the second embodiment, thecalculation of the expression (2) for calculating the inverter DCcurrent idc2 on the basis of the converter DC current idc1 and thecondenser current ic can be omitted as compared the embodiment of FIG.1.

Embodiment 3

A third embodiment of the power converter according to the presentinvention is shown in FIG. 8. The third embodiment is different from theembodiment of FIG. 1 in that the current detector 5 for directlydetecting the inverter DC current idc2 of the inverter circuit 2 isprovided instead of the current detector 4 for detecting the condensercurrent ic flowing through the smoothing condenser 10. Accordingly, thecondenser current ic flowing through the smoothing condenser 10 iscalculated on the basis of the converter DC current idc1 and theinverter DC current idc2 by the following expression (4).ic=idc 1−idc 2  (4)

According to the embodiment, the power converter 14 is characterized bythe configuration that is symmetrical about the smoothing condenser 10.Accordingly, the functions of the converter circuit 1 and the invertercircuit can be exchanged and accordingly even if the power supply isconnected to either of the converter circuit 1 and the inverter circuit2, the functions of the control means 22 of the converter circuit 1 andthe control means 23 of the inverter circuit 2 can be exchanged tothereby perform desired operation.

However, it is necessary to decide which of the converter circuit 1 andthe inverter circuit 2 the power supply is connected to before usualoperation. An example of the decision method is now described. In thefollowing description, an AC power supply is connected to the AC side ofthe converter circuit 1 and an AC load is connected to the AC side ofthe inverter circuit 2 in FIG. 8.

An example of the decision method performed just after turning on of thepower supply is now described with reference to FIG. 9. FIG. 9 shows awaveform 50 of a power-turned-on signal, a waveform 51 of the converterDC current idc1, a waveform 52 of the condenser current ic and awaveform 53 of the inverter DC current idc2. When the power converter 14is connected to the power supply in response to the power-turned-onsignal 50, an initial charging current flows through the smoothingcondenser 10. The initial charging current flows through the loopincluding AC power supply 6→reactor 7→diode connected ininverse-parallel to the semiconductor switching device of the upper armfor any phase→smoothing condenser 10→diode connected in inverse-parallelto the semiconductor device of the lower arm for any phase→reactor 7→ACpower supply 6. Accordingly, when currents are detected at a currentdetection timing 55 after a power-turned-on timing 54, the currentdetectors 3 and 4 can detect the currents 51 and 52 as shown in FIG. 9.That is, which of the current detectors 3 and 4 can detect a current isdecided to thereby make it possible to decide which of the convertercircuit 1 and the inverter circuit 2 the power supply is connected to.

On the other hand, when the smoothing condenser 10 is already charged,the method of FIG. 9 cannot make the decision. An example of thedecision method in this case is described with reference to FIGS. 10 to12. FIG. 10 shows a waveform of an on signal 70 of the lower arm of theconverter circuit 1, a waveform 71 of the converter DC current idc1, awaveform 72 of the condenser current ic and a waveform 73 of theinverter DC current idc2. The on signal 70 of the lower arm of theconverter circuit 1 is a signal that drives the semiconductor switchingdevices of the lower arms for the R-, S- and T-phases and when it ishigh level, the on signal 70 turns on the semiconductor switchingdevices. That is, the lower arms of all the phases of the convertercircuit 1 are turned on during an on period 74 of FIG. 10. At this time,for example, when the voltage for R-phase is highest and the voltagesfor S- and T-phases are negative, a current flows through the loopincluding AC power supply 6→reactor 91 for R-phase→semiconductorswitching device of lower arm for R-phase→semiconductor switchingdevices of lower arms for S- and T-phase→reactors 92 and 93 for S- andT-phases→AC power supply 6 as shown by solid line of FIG. 11. Thiscurrent stores energy in the reactors 7. Thereafter, when thesemiconductor switching devices of the lower arms for R-, S- andT-phases are turned off, a current flows through the loop including ACpower supply 6→reactor 91 for R-phase→semiconductor switching device 81(diode connected in inverse-parallel thereto) of the upper arm forR-phase→smoothing condenser 10→semiconductor switching devices of thelower arms for S- and T-phases→reactors 92 and 93 for S- and T-phases→ACpower supply 6 and the energy stored in the reactors 7 is moved to thesmoothing condenser 10. This current flows after the on period 74 asshown by the converter DC current (idc1) 71 and the condenser current(ic) 72 of FIG. 10. If an AC load is connected to the converter circuit1 instead of the AC power supply 6, no current flows even if thesemiconductor switching devices of the lower arms for R-, S- andT-phases are turned on and off. Accordingly, the current detection ismade at the current detection timing 75 after the on period 74, so thatit can be decided which of the converter circuit and the invertercircuit the power supply is connected to.

When the semiconductor switching devices of the lower arms for all thephases of the converter circuit 1 are turned on, the direction ofcurrents flowing through the reactors 91 to 93 for the respective phasesdepends on the phase of the AC power supply at the time that thesemiconductor switching devices of the lower arms are turned on, whileeven when the semiconductor switching devices of the lower arms areturned on at any time, the AC power supply 6 is short-circuited throughthe reactors 7 to store energy in the reactors 7 and the converter DCcurrent idc flows through the smoothing condenser 10 due to movement ofthe energy. Accordingly, the timing of the on period 74 of the lowerarms is not required to be prescribed particularly.

As described above, according to the embodiment, it is decided which ofthe converter circuit and the inverter circuit the AC power supply 6 isconnected to and the input/output relation of the converter controlmeans 22 and the inverter control means 23 can be exchanged after thedecision to thereby make operation even if which of the convertercircuit and the inverter circuit the power supply is connected to. Thatis, even if input/output wiring of the power converter 14 is made inerror, the power converter can be operated. Consequently, not only isthe freedom of wiring increased but also when the power converter 14 ofthe present invention is applied to a compressor driving system of apackaged-type air-conditioner, it is not necessary to change wiring whena power converter that is already installed in an outdoor unit of thepackaged-type air-conditioner is replaced. Particularly, maintenance canbe improved very effectively.

Embodiment 4

A fourth embodiment of the power converter according to the presentinvention is shown in FIG. 13. The fourth embodiment is different fromthe embodiment of FIG. 1 in that the current detector 5 for directlydetecting the inverter DC current idc2 of the inverter circuit 2 isprovided instead of the current detector 3 for detecting the converterDC current idc1. Accordingly, the converter DC current idc1 iscalculated on the basis of the condenser current ic flowing through thesmoothing condenser 10 and the inverter DC current idc2 by the followingexpression (5).idc 1=ic+idc 2  (5)

According to the embodiment, since electric power containing all lossesincluded in the smoothing condenser 10, the inverter circuit 2 and themotor 8 is inputted in the converter side, the converter DC current idc1is larger than the inverter side. Further, since only switching ripplesof the power converter circuit flow through the smoothing condenser 10basically, the absolute value of the current flowing through thesmoothing condenser 10 is very small as compared with the two powerconverter circuits. Accordingly, the configuration shown in theembodiment can be used to thereby reduce losses in the DC currentdetector on the converter side and improve the efficiency as comparedwith other embodiments.

Embodiment 5

FIG. 14 is a schematic diagram illustrating an outdoor unit 50 of anair-conditioner in which the power converter 14 of the present inventionis applied to drive a compressor thereof. The packaged-type powerconverter 501 is connected to a compressor 503 through wiring 502 anddrives a motor in the compressor 503 to compress refrigerant. Thecompressed high-pressure refrigerant passes through piping 504 and aheat exchanger 505 to radiate heat. Although not shown, there is anindoor unit paired with the outdoor unit 500. The refrigerant hasreduced pressure in a heat exchanger of the indoor unit to absorb heatand is returned to the compressor 503. The flow of the refrigerant inthe heating operation is reverse to that in the cooling operation andheat is radiated in a heat exchanger of the indoor unit in the heatingoperation. The power converter 14 is packaged to thereby facilitatemaintenance upon failure.

It should be further understood by those skilled in the art thatalthough the foregoing description has been made on embodiments of theinvention, the invention is not limited thereto and various changes andmodifications may be made without departing from the spirit of theinvention and the scope of the appended claims.

1. A converter comprising a converter circuit including a plurality ofbridge-connected semiconductor switching devices for converting AC powerinto DC power, a smoothing condenser connected in parallel to DC side ofsaid converter circuit and a condenser current detector provided in acondenser circuit to control a condenser current flowing through saidsmoothing condenser to be a set value.
 2. A converter according to claim1, comprising a controller for controlling said plurality ofsemiconductor switching devices to control said condenser current to besaid set value.
 3. A converter according to claim 2, wherein saidcontroller includes q-axis current control means for controlling aq-axis current component of DC output of said converter circuit toreduce a difference between said condenser current and said set value.4. A converter according to claim 3, comprising a DC current detectorfor detecting a DC current of said converter circuit and wherein saidcontroller includes calculation means for calculating an AC current oninput side of said converter circuit on the basis of said DC current andoperation states of said plurality of semiconductor switching devicesand compensation means for calculating a q-axis current component ofsaid AC current to correct a q-axis current command value on the basisof said calculated q-axis current component.
 5. A converter according toclaim 4, wherein said condenser current detector and said DC currentdetector each include a shunt resistor.
 6. A converter of packaged typecomprising a main circuit board in which a converter circuit including aplurality of bridge-connected semiconductor switching devices forconverting AC power into DC power is formed, a controller board in whicha controller for controlling said plurality of semiconductor switchingdevices is formed, a package in which said main circuit board isprovided and on which said controller board is placed to connecttherebetween, an external terminal for a smoothing condenser connectedin parallel to DC side of said converter circuit and which is mounted atperiphery of said package and a condenser current detector connectedbetween said external terminal and said converter circuit.
 7. Aconverter of packaged type according to claim 6, wherein said controllerincludes current control means for controlling said plurality ofsemiconductor switching devices to control a condenser current flowingthrough said smoothing condenser to be a set value.
 8. A converter ofpackaged type according to claim 7, wherein said current control meansincludes q-axis current control means for controlling a q-axis currentcomponent on DC side of said converter circuit to reduce a differencebetween said condenser current and said set value.
 9. A converter ofpackaged type according to claim 8, comprising a DC current detector fordetecting a DC current of said converter circuit and wherein saidcontroller includes calculation means for calculating an AC current oninput side of said converter circuit on the basis of said DC current andoperation states of said plurality of semiconductor switching devicesand compensation means for calculating a q-axis current component ofsaid AC current to correct a q-axis current command value on the basisof said calculated q-axis current component.
 10. A converter of packagedtype according to claim 9, wherein said condenser current detector andsaid DC current detector each include a shunt resistor.
 11. A converterof packaged type comprising a main circuit board in which two sets ofpower converter circuits each including a plurality of bridge-connectedsemiconductor switching devices are connected to each other through a DCcircuit, a controller board in which a controller for controlling saidplurality of semiconductor switching devices for said two sets of powerconverter circuits is formed and a package in which said main circuitboard is provided and on which said controller board is placed toconnect therebetween, said package including two sets of AC terminalsconnected to said two sets of power converter circuits, respectively, anexternal terminal for a smoothing condenser connected in parallel tosaid DC circuit and an external terminal connected to said controller,all said terminals being disposed at periphery of said package, saidmain circuit board including at least two current detectors fordetecting a DC current flowing through said external terminal for saidsmoothing condenser and DC currents in said power converter circuits.12. A power converter of packaged type according to claim 11, whereinsaid controller includes current calculation means for calculating acurrent in a part where said current detector is not provided on thebasis of two detected current values detected by said two currentdetectors.
 13. A power converter of packaged type according to claim 11,wherein said controller controls said plurality of semiconductorswitching devices for one of said two sets of power converter circuitsso that said DC current flowing through the external terminal for saidsmoothing condenser is controlled to be a set value.
 14. A powerconverter of packaged type according to claim 11, wherein said at leasttwo current detectors each include a shunt resistor.
 15. A powerconverter of packaged type according to claim 14, wherein said at leasttwo shunt resistors each have one terminal connected to the samepotential.
 16. A power converter of packaged type according to claim 11,wherein said controller includes decision means for deciding an ACterminal connected to an AC power supply on the basis of a detectedcurrent of said at least one current detector and means for controllingto operate said power converter circuit connected to said AC powersupply as a converter and to operate the other power converter circuitas an inverter on the basis of decision result of said decision means.17. A power converter of packaged type according to claim 11, whereinsaid controller includes decision means for deciding an AC terminalconnected to an AC power supply on the basis of a detected current ofsaid at least one current detector after said semiconductor switchingdevices of lower arms for one of said two sets of power convertercircuits are turned on and means for controlling to operate said powerconverter circuit connected to said AC power supply as a converter andto operate the other power converter circuit as an inverter on the basisof decision result of said decision means.
 18. An air-conditionercomprising said power converter of packaged type according to claim 11and a motor of a compressor that is driven by said power converter.